This invention relates to method of connecting a semiconductor device to a wiring board, and more particularly to method of readily connecting electrodes of a semiconductor device to wiring pattern of a wiring board.
Recently, development of a device or piece of equipment in which many semiconductor devices are used has been facilitated. Examples of such devices are a memory card, a liquid crystal display panel, an electroluminescence display panel and so on. In these devices, many ICs and LSIs have to be disposed or mounted on a substrate of predetermined size. This must be done with relatively high density and in an ever thinner fashion.
As to methods which are used for mounting IC or LSI on a substrate, there are flip chip and tape carrier systems, each of which has the following drawbacks. In these flip chip and tape (film) carrier systems used as a semiconductor mounting method, metal projections or metal bumps are provided on electrode pads of a semiconductor device.
A relevant method of which this inventor is one the joint inventors is set forth in U.S. Pat. No. 4,494,688 to Hatada et al., entitled "Method of connecting metal leads with electrodes of semiconductor devices and metal lead therefor".
In the flip chip system, metal bumps are aligned with wiring pattern on a wiring board and then, heated to be melted sufficiently so that metal bumps are fixed to the wiring pattern. In the case of such flip chip systems, the electrical connection of a semiconductor device and wiring pattern, and the fixing of a semiconductor device on a wiring board are achieved by metal bumps or solder. Therefore, if a mounting surface of a wiring board has some twisted or curved portion and a semiconductor device is mounted and fixed on such twisted or curved surface portion through a metal bump connection, it may occur that the a semiconductor device itself or a metal bump connection is destroyed by unnecessary force owing to the twisted or curved surface portion.
On the other hand, in the case of tape carrier system, metal bumps of a semiconductor device are connected to the wiring pattern of a wiring board through flexible leads or film leads so that the above-stated unnecessary force owing to the twisted or curved surface portion may be absorbed by the flexibility of the film leads. However, this system requires film leads which increase mounting cost. Also, the area necessary for mounting increases because film leads project from the mounting surface of a semiconductor device.
As stated above, in conventional flip chip and tape carrier systems having a semiconductor device mounted by the above method, there may occur several disadvantages such as the semiconductor device itself or a connection portion of the wiring pattern and semiconductor device being destroyed owing to unnecessary induced forces. Also, the mounting cost and area size become undesirably large.